"Tactical" /24 announcements

Wed Aug 11 13:09:59 UTC 2021

On Wed, 11 Aug 2021, Tom Hill wrote:

> On 10/08/2021 07:15, Lukas Tribus wrote:
>>> Are there any big networks that drop or penalize announcements like this?
>> It's possible you could get your peering request denied for this. I
>> have put *reasonable* prefix aggregation into peering requirements for
>> some years now. If you are a small eyeball network with 8192 IP
>> addresses and originate 32 /24's, that is *not* reasonable.
>
> It is quite an issue when a network tries to programmatically filter-out
> the /24 more-specifics advertisements made from an allocated, .e.g, /20.
>
> Such anti-disaggregation/save-my-TCAM efforts really do not work, and
> will spawn all manner of support tickets. I'm saying this in the hope
> that it may prevent someone from reading this thread and concluding that
> it may be a good idea to try. It is not.

What sort of hands-on experience is this opinion based on?

I've done this manually in the past (quite some time ago), and done 
properly, it works fine.

At least one major network hardware vendor has implemented it as a 
feature.  Turn it on, and the "deaggregates" with same next-hop as an 
aggregate are not programmed into the FIB.  The savings will vary 
depending on the device's connectivity, but I've seen >40%.

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